Purpose: The welfare reform bill of 1996 severely constrained noncitizens' eligibility for the Food Stamp Program (FSP). This study examined the effects of eligibility restrictions on older immigrants' FSP participation and food insecurity. We paid special attention to household composition and household eligibility as well as older immigrants' individual eligibility. Design and Methods: The sample consisted of 3,175 low-income older adults from the 1999 Current Population Survey. We used probit and tobit regressions. We compared three analytical models: two models using the differences-in-differences approach with two different measures of immigration status (individual and household status), and one using a summary variable of the percentage of FSP-eligible people in a household. Results: Both household immigration status and older adults' individual immigration status were significantly associated with the probability of FSP participation. Living in a household with a higher percentage of eligible members significantly increased older people's FSP participation and benefit levels while significantly reducing their risk of food insecurity. Implications: Noncitizen eligibility restriction affects older immigrants' FSP participation and food insecurity by its relation to household composition. Experts should therefore consider household composition when developing social policies for older immigrants.